An important aspect of many MEMS (or many other electronic chip) devices is the development and execution of efficient, robust, and protective packaging strategies. Typically a wafer containing many MEMS devices is cut into a number of MEMS die, which are then individually packaged using relatively complex and labor intensive processes. For many MEMS devices, particularly those using moving features such as cantilever beams or other suspended structures, there is a desire to create a well-contained and controlled environment such as a vacuum environment. Such packaging often includes a cavity formed by a chip carrier and a lid. A getter is sometimes provided in the cavity to capture gasses that enter the cavity through out gassing and/or small leakage paths.
Typically, each MEMS device is secured to a chip carrier via solder, adhesive, or in some other way. This mechanically secures the MEMS device to the chip carrier, and is often performed using a conventional die bonding machine. One such die bonding machine is the Automatic Component Assembly Cell 3500-II, available from Palomar Technologies, Inc., located in Vista, Calif. Once the MEMS device is secured to the chip carrier, the I/O pads on the MEMS device are electrically wired to pads on the chip carrier. This is often performed using a conventional wire bonding machine. One such wire bonding machine is the Model 2460-V Automatic Wire Bonder, also available from Palomar Technologies. When flip-chip bonding is used, ball bonds or the like may be used to both secure the MEMS device to the package and to electrically connect the I/O pads of the MEMS device to pads on the chip carrier, as is known in the art.
Next, a solder ring or the like is often placed on the chip carrier. The solder ring will eventually be used to solder the lid to the chip carrier to create a vacuum seal for the enclosed MEMS device. In many cases, the chip carrier assembly is baked in a vacuum environment for some time to cause the materials used in the chip carrier assembly to outgas as much as possible.
A getter may be spot welded or otherwise attached to the package lid. The chip carrier assembly and the lid are then typically placed in a vacuum chamber, and heat is applied to activate the getter. Once the getter is activated, the lid is brought into alignment with the chip carrier assembly, and heat and pressure are applied so that the solder ring secures and seals the lid to the chip carrier assembly, thereby providing a vacuum environment for the enclosed MEMS device.
In many cases, the above process steps are performed in a manual or semi-automated way. Some of the steps may be performed using some batch process techniques and/or some automated equipment. However, significant manual handling of the parts is still often required. What would be desirable, therefore, is a more automated process for packaging MEMS devices.